Color reversal photographic light-sensitive materials are generally color photographic light-sensitive materials containing at least three silver halide emulsions each having a different light-sensitivity (typically layers sensitive to light in three regions in the visible light spectrum, namely, red, green or blue). The layers generally contain three color formers (couplers) of cyan, magenta and yellow, which form a positive image by color reversal processing after exposure to light. Color reversal processing generally includes a first development step (black and white development) and subsequent steps of reversal, color development, bleaching and fixation, as in Fuji Processing CR-56. The mechanism of color reversal processing has been explained in detail in, e.g., T. H. James, The Theory of the Photographic Process, pages 335-338 (McMillan, 4th ed. 1977).
A determination of the quality of color positive images obtained by color reversal processing of a color reversal light-sensitive material is preferably carried out by taking photographs of various objects. However, a method based upon characteristic curves in which image densities of each light-sensitive material are shown as functions of exposure amount, and evaluating the quality of color positive images using the shape of these characteristic curves, is ordinary used as a substitute by persons skilled in the art.
As described in Eiji Hozumi, Sensitometry no Jissai, page 156 (1st ed. October, 1970) in color reversal photographic light-sensitive materials, color reproduction characteristics and tone reproduction characteristics of an image are determined by the gradation of characteristic curves of three colors of cyan, magenta and yellow and the balance of gradation among the three colors. Particularly, the gradation of the low density section (i.e., in a reversal image) in the characteristic curve has a great influence upon color reproduction characteristics and tone reproduction characteristics. In conventional color reversal photographic light-sensitive materials, since gradation of the low density section is too soft, reduction of density corresponding to increase of the exposure amount is insufficient, resulting in the disadvantage that only an impure white color having a high density is obtained by reproduction in the color image, although the object to be photographed is white.
Various efforts have been made to improve the color reproduction characteristics of color reversal photographic light-sensitive materials, but they can not improve the gradation of the low density section in the above described characteristic curves to provide a sufficiently hard tone. For example, a technique of improving color brilliancy by an integrated layer effect, i.e., by providing a silver halide emulsion layer spectrally sensitized in a spectral region different from the adjacent light-sensitive silver halide emulsion layer (for example, a red-sensitized light sensitive halide emulsion layer which is subjected to gold sensitization, provided on a blue-sensitive emulsion layer) in the color reversal photographic light-sensitive materials is described in U.S. Pat. No. 3,728,121. However, gradation of the low density section of the characteristic curves is not improved to provide a hard tone by this technique.
An object of the present invention is to provide color reversal photographic light-sensitive materials having improved gradation of the low density section of the characteristic curves or reversal image, i.e., a hard tone and improved reduction of density corresponding to increase of the exposure amount.
In attempting to improve color reproduction characteristic, the persent inventors have attempted to use a silver halide emulsion layer having substantially no light-sensitivity provided adjacent to the light-sensitive silver halide emulsion layer in the color reversal photographic light-sensitive material either directly or with an intermediate layer. By this means, it was expected that gradation of the low density section of the characteristic curves of the reversal image could be improved so as to have a hard tone by trapping halogen ions formed by the first development of the light-sensitive silver halide emulsion (this halogen ion is easily formed in high exposure areas, i.e., those corresponding to the low density section of the characteristic curve of the reversal image) with silver halide emulsion grains having substantially no light-sensitivity to reduce development restraint of the light-sensitive silver halide emulsion caused by the presence of this halogen ion (i.e., to accelerate development).
However, unexpectedly it was discovered that gradation of the low density section of the characteristic curve obtained with this material after complete color reversal development processing was not improved as compared with the prior color reversal photographic light-sensitive materials in which the silver halide emulsion layer having substantially no light-sensitivity was absent.
As a result of further minute analyses and experiments, it was discovered that, in the course of complete color reversal processing, residual emulsion grains which were not developed by the first development step in the auxiliary silver halide emulsion layer (i.e., having substantially no light-sensitivity) provided centers of development on their surfaces in subsequent reversal development steps after the first development step. Because of this, the auxiliary emulsion was changed into an emulsion capable of contributing to color formation in color development. If a dye forming coupler containing layer is present near this auxiliary layer, an oxidation product of a developing agent formed by development of the substantially insensitive silver halide emulsion in the auxiliary layer, which does not essentially contribute to formation of an image, nonetheless has some influence upon color formation of the dye forming coupler containing layer. For this reason, the expected results were not obtained.